1. Field of the Invention
The present invention relates to a sheet discharging apparatus used in an image forming apparatus such as, for example, a copier, a printer, a facsimile and the like and an image forming apparatus having such a sheet discharging apparatus, and more particularly, it relates to a compact sheet discharging apparatus having good operability and an image forming apparatus having such a compact sheet discharging apparatus.
2. Description of the Related Art
Recently, in image forming apparatuses such as printers, copiers and the like, needs for miniaturizing a main body or frame of the image forming apparatus have particularly been increased. Particularly, in a color image forming apparatus, since an image forming portion tends to become bulky, compactness thereof has been requested strongly.
Further, regarding operability of the main body of the image forming apparatus, particularly, needs for improving a jam treatment ability and exchangeability of a process cartridge has been increased, and thus, it is very important to perform such operations by one-action.
In order to satisfy such requirements, for example, in a color image forming apparatus described in Japanese Patent Application Laid-Open No. 2001-34021, as shown in FIG. 9, process cartridges Y, M, C and K capable of forming respective color images are arranged in an up-and-down (vertical) direction and the jam treatment and the exchanging of the process cartridge can be facilitated by opening a front cover 100. Further, the jam treatment in a fixing portion and a sheet discharging portion can be performed by opening an upper cover 101. In this way, by providing a front-operation structure in which the jam treatment and the exchanging of the process cartridge can be completed only at a front side of the main body of the image forming apparatus, the operability of the operator can be improved.
However, since the plurality of process cartridges are arranged in the vertical direction, there arises a problem that a height of the main body of the apparatus becomes relatively great, and thus, a technique for reducing such height as less as possible is required.
To this end, it is considered to design an arrangement in which a discharged sheet full-stacked condition detecting portion does not affects an influence upon the height of the main body by attaching a lever member 102 constituting the discharged sheet full-stack condition detecting portion for the sheets discharged on a discharge tray 103 to the opening/closing upper cover 101.
However, in the above-mentioned arrangement, if the sheets are stacked up to a substantially full-stack condition, for example as shown in FIG. 9, when the upper cover 101 supported by an L-shaped arm 105 rotatable around an rotation axis 104 tries to be closed, the lever member 102 may be caught by the stacked sheets. As shown in FIG. 10, when the lever member 102 is lowered by its own weight, the lever member is locked by a stopper (not shown) provided on the upper cover 101, thereby preventing a further rotation of the lever member in an anti-clockwise direction. The reason is that, when a sheet P1 is discharged from the main body of the image forming apparatus, an angle between the lever member 102 and the upper cover 101 is maintained to a predetermined angle range to prevent the buckling of the sheet even if a leading end of the sheet P1 abuts against the lever member 102.
Further, since the rotation axis 104 of the upper cover 101 does not coincide with a rotation center of the lever member 102, the following influences occur. That is to say, as shown in FIGS. 11A to 11C, from a condition that the upper cover 101 is opened, as the upper cover is closed, due to the rotation of the upper cover 101, the lever member 102 is shifted obliquely and downwardly to approach a pair of discharge rollers 106. Further, from the condition that the upper cover 101 is opened, as the upper cover is closed, the lever member 102 remains in a suspended condition halfway due to its own weight (see FIGS. 11A and 11B). However, when the lever member 102 is engaged by the stopper of the upper cover 101, the lever member 102 is lifted by the stopper to be rotated together with the upper cover 101 (see FIG. 11B). In this case, as shown in FIG. 11C, a leading end of the lever member 102 may be caught by the sheet stack P1 not to permit the closing of the upper cover.